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1
Biochemistry of Cells
Copyright Cmassengale
2
Water
Water is used in most reactions in the bodyWater is called the universal solvent
Copyright Cmassengale
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Carbon-based MoleculesOrganic chemistry is the study of carbon compounds
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Carbon is a Versatile AtomIt has four electrons in an outer shell that holds eight
Carbon can share its electrons with other atoms to form up to four covalent bonds
Copyright Cmassengale
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Hydrocarbons
The simplest carbon compounds …Contain only
carbon & hydrogen atoms
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Shape of Organic Molecules
Each type of organic
molecule has a unique three-dimensional
shapeThe shape determines its function in an
organism
Copyright Cmassengale
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Functional Groups are:
Groups of atoms that give properties to the compounds to which they attach
Gained Electrons Lost ElectronsCopyright Cmassengale
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Giant Molecules - Polymers
Large molecules are called polymersPolymers are built from smaller molecules called monomersBiologists call them macromolecules
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Examples of Polymers
Proteins
Lipids
Carbohydrates
Nucleic Acids
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Most Macromolecules are Polymers
Polymers are made by stringing together many smaller molecules called monomers
Nucleic Acid
Monomer
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Linking Monomers
Cells link monomers by a process
called condensation or dehydration synthesis (removing a molecule of
water)
This process joins two sugar monomers to make a double
sugar
Remove H
Remove OH
H2O Forms
Copyright Cmassengale
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Breaking Down PolymersCells break
down macromolecules by a process called hydrolysis (adding a molecule of water) Water added to split a double
sugarCopyright Cmassengale
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Macromolecules in Organisms
There are four categories of large molecules in cells:
Carbohydrates
Lipids
Proteins
Nucleic Acids
Copyright Cmassengale
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Carbohydrates
Carbohydrates include:
Small sugar molecules in soft
drinksLong starch
molecules in pasta and potatoes
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Monosaccharides:
Called simple sugarsInclude glucose,
fructose, & galactoseHave the same chemical, but different structural formulas
C6H12O6
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Monosaccharides
Glucose is found in sports drinks
Fructose is found in fruitsHoney contains both glucose & fructoseGalactose is called “milk sugar”
-OSE ending means SUGARCopyright Cmassengale
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Cellular Fuel
Monosaccharides are the main fuel that cells use for cellular work
ATP
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Disaccharides
A disaccharide is a double sugar
They’re made by joining two monosaccharidesInvolves removing a water molecule (condensation)
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Polysaccharides
Complex carbohydrates
Composed of many sugar monomers linked togetherPolymers of monosaccharide chains
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Examples of Polysaccharides
Starch
Glycogen
Cellulose
Glucose Monomer
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Sugars in Water
Simple sugars and double sugars dissolve readily in water
They are hydrophilic, or “water-loving”
WATER MOLECULE
SUGAR MOLECULE
-OH groups make them water soluble
Copyright Cmassengale
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Lipids
Lipids are hydrophobic –”water fearing”
Includes fats, waxes, steroids, & oils
Do NOT mix with water
FAT MOLECULE
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Function of Lipids
Fats store energy, help to insulate the body, and cushion and protect organs
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Types of Fatty Acids
Unsaturated fatty acids have less than the maximum number of hydrogens bonded to the carbons (a double bond between carbons)
Saturated fatty acids have the maximum number of hydrogens bonded to the carbons (all single bonds between carbons)
Copyright Cmassengale
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Triglyceride
Monomer of lipids
Composed of Glycerol & 3 fatty acid chainsGlycerol forms the “backbone” of the fat Organic
Alcohol (-OL ending)
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Fats in Organisms
Most animal fats have a high proportion of saturated fatty acids & exist as solids at room temperature (butter, margarine, shortening)
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Fats in Organisms
Most plant oils tend to be low in saturated fatty acids & exist as liquids at room temperature (oils)
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Fats
Dietary fat consists largely of the molecule triglyceride composed of glycerol and three fatty acid chains
Glycerol
Fatty Acid Chain
Condensation links the fatty acids to Glycerol
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Lipids & Cell Membranes
• Cell membranes are made of lipids called phospholipids
• Phospholipids have a head that is polar & attract water (hydrophilic)
• Phospholipids also have 2 tails that are nonpolar and do not attract water (hydrophobic)
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Proteins
Proteins are polymers made of monomers called amino acids
Proteins are used to build cells, act as hormones & enzymes, and do much of the work in a cell
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Linking Amino Acids
Cells link amino acids together to make proteinsThe process is called condensation or dehydrationPeptide bonds form to hold the amino acids together
Carboxyl
Amino Side
Group
Dehydration Synthesis
Peptide Bond
Copyright Cmassengale
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Proteins as Enzymes
Many proteins act as biological catalysts or enzymes
Thousands of different enzymes exist in the body
Enzymes control the rate of chemical reactions by weakening bonds, thus lowering the amount of activation energy needed for the reaction
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Enzymes
Their folded conformation creates an area known as the active site.
Enzymes are globular proteins.
The nature and arrangement of amino acids in the active site make it specific for only one type of substrate.
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Protein Structures or CONFORMATIONS
Hydrogen bond
Pleated sheet
Amino acid
(a) Primary structure
Hydrogen bond
Alpha helix
(b) Secondary structure
Polypeptide(single subunit)
(c) Tertiary structure
(d) Quaternary structure
Copyright Cmassengale
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Denaturating Proteins
Changes in temperature & pH can denature (unfold) a protein so it
no longer worksCooking denatures protein in eggs
Milk protein separates into curds & whey when it denatures
Copyright Cmassengale
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Changing Amino Acid Sequence
Substitution of one amino acid for another in hemoglobin causes
sickle-cell disease
(a) Normal red blood cell Normal hemoglobin
12 3
4 56
7. . . 146
(b) Sickled red blood cell Sickle-cell hemoglobin
2 314 5
67. . . 146
Copyright Cmassengale
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Other Important Proteins
•Blood sugar level is controlled by a protein called insulin
•Insulin causes the liver to uptake and store excess sugar as Glycogen
•The cell membrane also contains proteins
•Receptor proteins help cells recognize other cells
Copyright Cmassengale
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Nucleic Acids
Store hereditary information
Contain information for making all the body’s proteinsTwo types exist --- DNA & RNA
Copyright Cmassengale
39 Copyright Cmassengale
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Nucleic AcidsNitrogenous base
(A,G,C, or T)
Phosphategroup
Thymine (T)
Sugar(deoxyribose)
Phosphate
BaseSugar
Nucleic acids are polymers of nucleotides
Nucleotide
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Nucleotide – Nucleic acid monomer
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Bases
Each DNA nucleotide has one of the following bases:
Thymine (T): pyrimidine
Cytosine (C): pyrimidine
Adenine (A): purine
Guanine (G):purine
–Adenine (A)
–Guanine (G)
–Thymine (T)
–Cytosine (C)
Copyright Cmassengale
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Nucleotide Monomers
Form long chains called DNA
Backbone
Nucleotide
Bases
DNA strand
Nucleotides are joined by sugars & phosphates on the side
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DNA
Two strands of DNA join together to form a double helix
Basepair
Double helix
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RNA – Ribonucleic Acid
Ribose sugar has an extra –OH or hydroxyl groupIt has the base uracil (U) instead of thymine (T)
Nitrogenous base(A,G,C, or U)
Sugar (ribose)
Phosphategroup
Uracil
Copyright Cmassengale
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ATP – Cellular Energy
•ATP is used by cells for energy
•Adenosine triphosphate
•Made of a nucleotide with 3 phosphate groups
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Summary of Key Concepts
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Nucleic Acids
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Macromolecules
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Macromolecules
Copyright Cmassengale
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End
Copyright Cmassengale
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